Sheet metal manufacturers typically produce sheets of metal material in coiled form having a substantial width. Before such coiled metal can be used for certain fabrication purposes, it must be cut by a slitter into strips or strands of desired width and recoiled for shipping and handling. The typical slitting apparatus has an uncoiler, a slitter and a recoiler. The coiled sheet is uncoiled and passed through the slitter to form a plurality of individual strands. These individual strands are then wound onto a mandrel or drum on the recoiler to form a plurality of individual coils. U.S. Pat. Nos. 3,406,924 and 4,093,140, the entire disclosures of which are each hereby incorporated by reference, disclose a recoiler in the slitting apparatus that utilizes a diametrically expandable mandrel for winding the coils thereon. The mandrel retracts or collapses so that the coils can be easily removed therefrom. These mandrels also commonly employ a clamping slot or other gripping means to secure the leading ends of the strips. U.S. Pat. No. 3,406,924 also discloses the use of cylindrical cores placed on the mandrel that are frictionally driven by the mandrel and provide relative rotation or slip as required to maintain a tension in each of the individual strips according the varying thicknesses among the strips.
The conventional mandrels used in slitting machines are available with standard outer diameters, such as 6 inches or 24 inches in the expanded position. The recoiled strips will have an inner diameter equal to the outer diameter of the expanded mandrel. If coils with an inner diameter other than a standard dimension are desired by a customer for a particular application, a mandrel of the desired nonstandard diameter must be mounted on the sheet metal slitting apparatus. Mandrels, particularly expandable mandrels, are complex and costly to manufacture, and in addition, mandrels of nonstandard diameters require new forgings and patterns. If the quantity of slit metal for a particular customer application does not justify the cost of manufacturing a new, special mandrel, the sheet metal slitter may be unable to satisfy the customer's request.
There is thus a need to develop an inexpensive means for a sheet metal slitter to adjust the size of the inner diameter of the coils.